Method and device for interleaving data

ABSTRACT

Embodiments of this application provide a method for processing information bits in a wireless communication network. A device obtains a Polar encoded bit sequence, then divide the Polar encoded bit sequence into g groups that are of equal length N/g, wherein g is 32. The device block interleaves the g groups to obtain an interleaved bit sequence according to a sequence S, wherein the sequence S comprises: group numbers of the g groups, wherein a group whose number is 0 is the first element in the sequence S, wherein a group whose number is 12 is the 17th element in the sequence S, wherein a group whose number is 31 is the 32nd element in the sequence S, wherein the S is an integer and output the interleaved bit sequence.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/796,300, filed on Feb. 20, 2020, which is a continuation of U.S.patent application Ser. No. 16/406,860, filed on May 8, 2019, now U.S.Pat. No. 10,608,668, which is a continuation of InternationalApplication No. PCT/CN2018/091835, filed on Jun. 19, 2018, which claimspriority to Chinese Patent Application No. 201710459439.4, filed on Jun.16, 2017. All of the afore-mentioned patent applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments disclosed herein relate to the field of communicationtechnologies, and in particular, to a method and device for interleavingdata.

BACKGROUND

Channel encoding is used in communication systems to improve datatransmission reliability, so as to ensure communication quality. A polarcode, proposed by Professor Arikan of Turkish, is the first code thatare theoretically proven to be able to achieve the Shannon capacity andhaving low encoding and decoding complexity. The polar code is a linearblock code. A encoding matrix of the polar code is G^(N), which is anN×N matrix. An encoding process for generating a polar code x₁ ^(N) isx₁ ^(N)=u₁ ^(N)G_(N), where u₁ ^(N)=(u₁, u₂, . . . , u_(N)) is a binaryrow vector having a length is N (N is also called a mother code length),and G_(N)=F₂ ^(⊗(log) ² ^((N))). F₂ ^(⊗(log) ² ^((N)))is a Kroneckerproduct of log₂ N matrices F₂, and the matrix F₂ is:

$F_{2} = {\begin{bmatrix}1 & 0 \\1 & 1\end{bmatrix}.}$

In the encoding process of the polar code, some bits in the row vectoru₁ ^(N) are used to carry information and these bits are referred to asinformation bits. An index set of the bits is represented as A. Theother bits are set to a fixed value that is pre-agreed upon between atransmitting end and a receiving end of the polar code, and these bitsare referred to as fixed bits or frozen bits. An index set of these bitsis represented by

^(c), which is a complementary set of

. The polar encoding process of the polar code is equivalent to x₁^(N)=u_(A)G_(N)(A)⊗u_(A) _(c) G_(N)(A^(C)). Herein, G_(N) (A) is asubmatrix formed by rows in the G_(N) that correspond to indexes in theset A, and G_(N) (A^(C)) is a submatrix formed by rows in the G_(N) thatcorrespond to indexes in the set A^(C).

is an information bit set of the u₁ ^(N), and the number of theinformation bits is K; and u_(A) _(c) is a frozen bit set of the u₁^(N), the number of frozen bits is (N−K), and the frozen bits are knownbits. Value of the frozen bits is normally set to 0, but the value ofthe frozen bits may be randomly set, provided that the transmitting endand the receiving end of the polar code have pre-agreed on the value ofthe frozen bits. When the frozen bits are set to 0, a polar codeencoding output may be simplified as follows: x₁ ^(N)=

G_(N)(

), in which G_(N) (A) is a K×N matrix.

A process of constructing polar code is a process of selecting the set

, and the selection of the set A determines performance of the polarcode. The process of constructing polar code is usually as follows:determining, based on a mother code length N, that a total of Npolarized channels, where each of the N polarized channels respectivelycorrespond to one row in an encoding matrix, respectively; calculating areliability of each of the polarized channels; and forming theinformation bit index set A using indexes of first K polarized channelswith relatively high reliability, and forming the frozen bit index set

^(c) using indexes of the remaining (N−K) polarized channels. The set Adetermines bit positions of the information bits in x₁ ^(N), and the set

^(c) determines bit position of the frozen bits in x₁ ^(N).

It can be learned from the encoding matrix that a code length of anoriginal polar code (mother code) is an integral power of 2. Inpractical applications, however, length of a polar code need to be setto any code length, and this is achieved by a process called ratematching.

SUMMARY

Embodiments of the application provides a method, an apparatus for ratematching, to implement a polar code with any code length.

According to a first aspect, embodiments of this application provide amethod for a rate matching. The method includes:

-   -   obtaining a first encoded bit sequence, where the first encoded        bit sequence includes g groups that are of equal length, a        quantity of each group is N/g, N is a length of mother code of a        polar code, N is an integral power of 2, g is an integer greater        than or equal to 4 and less than N, and g is an integral power        of 2,    -   determining, based on the groups, a bit position of a bit that        needs to be punctured/shortened in the encoded bit sequence; and    -   obtaining a second encoded bit sequence after removing the bit        that needs to be punctured/shortened from the first encoded bit        sequence, wherein the second encoded bit sequence is a bit        sequence obtained after rate matching.

According to a second aspect, embodiments of this application provide anapparatus for rate matching, including:

-   -   an obtaining unit, configured to obtain a first encoded bit        sequence, where the encoded bit sequence includes g groups that        are of equal length, a quantity of each group is N/g, N is a        length of mother code, N is an integral power of 2, g is an        integer greater than or equal to 4 and less than N, and g is an        integral power of 2;    -   a first determining unit, configured to determine, based on the        groups, a bit position of a bit that needs to be        punctured/shortened in the first encoded bit sequence; and    -   a rate matching unit, configured to obtain a second encoded bit        sequence after removing the bit that needs to be        punctured/shortened from the first encoded bit sequence, wherein        the second encoded bit sequence is a bit sequence obtained after        rate matching.

With reference to the first aspect, in a possible implementation,embodiments of this application further includes:

-   -   a second determining unit, configured to: when an actual code        rate is greater than a preset threshold, rate matching manner is        a shortening; or when the actual code rate is less than or equal        to a preset threshold, rate matching manner is a puncturing,        where the actual code rate is K/N, K is a length of information        bits, and M is a length of target code.

With reference to the first aspect, in a possible implementation,embodiments of this application further includes:

-   -   an encoding unit, configured to: place a frozen bit in a        polarized channel corresponding to the bit position of the bit        that needs to be punctured/shortened; in remaining polarized        channels, select a polarized channel with high reliability,        place an information bit in the polarized channel with high        reliability, and place frozen bits on the other polarized        channels; and encode a to-be-coded bit by channel coding, to        obtain the first encoded bit sequence.

According to a third aspect, a rate matching apparatus is provided,including:

-   -   a memory, configured to store a program; and    -   a processor, configured to execute the program stored in the        memory, where when the program is executed, the processor is        configured to perform the method for rate matching provided in        the first aspect of the embodiments of this application.

According to a fourth aspect, embodiments of this application provide amethod for a rate de-matching including:

-   -   obtaining a log-likelihood ratio (LLR) of a to-be-decoded bit        sequence, to obtain an LLR bit sequence;    -   determining a bit position of puncturing/shortening based on        groups; and    -   obtaining an LLR sequence according to an LLR value of a bit at        the bit position of puncturing/shortening, where the LLR        sequence includes g groups that are of equal length, a quantity        of each group is N/g, N is a length of mother code of a polar        code, N is an integral power of 2; g is an integer greater than        or equal to 4 and less than N, and g is an integral power of 2.

According to a fifth aspect, embodiments of this application provide anapparatus for a rate de-matching, including:

-   -   an obtaining unit, configured to obtain a log-likelihood ratio        (LLR of a to-be-decoded bit sequence;    -   a determining unit, configured to determine a bit position of        puncturing/shortening based on groups; and    -   a rate de-matching unit, configured to obtain an LLR sequence        according to an LLR value of a bit position of        puncturing/shortening, where the LLR sequence includes g groups        that are of equal length, a quantity of each group is N/g, N is        a length of mother code of a polar code, N is an integral power        of 2, g is an integer greater than or equal to 4 and less than        N, and g is an integral power of 2.

According to a sixth aspect, embodiments of this application provide anapparatus for rate de-matching, including:

-   -   a memory, configured to store a program; and    -   a processor, configured to execute the program stored in the        memory, where when the program is executed, the processor is        configured to perform the method for rate de-matching in the        fourth aspect and all possible implementations of the rate        de-matching method.

With reference to any one of the first to the sixth aspects, in apossible implementation, the determining, based on the groups, a bitposition of a bit that needs to be punctured/shortened in the firstencoded bit sequence includes:

-   -   determining, based on the groups and a puncturing pattern or        shortening pattern, the bit position of the bit that needs to be        punctured/shortened in the first encoded bit sequence,        puncturing/shortening a priority order of puncturing/shortening        the g groups is determined according to the        puncturing/shortening pattern.

In a possible implementation, a reverse relationship exists between thepuncturing pattern and the shortening pattern.

In another possible implementation, the puncturing/shortening patternincludes: successively determining, based on the respectively priorityorder of puncturing/shortening, bit positions of bits that need to bepunctured/shortened in all the groups.

In another possible implementation, the puncturing/shortening patternincludes: successively determining, based on a priority order of thegroups, bits that need to be punctured/shortened from bits in groupswith different priorities, and successively determining, in an alternatemanner, bits in different groups with a same priority as bit positionsof bits that need to be punctured/shortened.

In another possible implementation, the puncturing/shortening pattern isindicated by a sequence S, elements in the sequence S include groupnumbers of the g groups that are ordered based on the priority order ofpuncturing/shortening the g groups, and bit positions of first g/2groups in the sequence S are symmetrical to bit positions of last g/2groups in the sequence S.

In another possible implementation, the puncturing/shortening pattern isindicated by a sequence S, and elements in the sequence S include groupnumbers of the g groups that are sorted based on the priority order ofpuncturing/shortening the g groups, where

-   -   the sequence S is a sequence based on a natural order, a        bit-reversal order, a reliability order, or a code weight order        of polarized channels when the mother code length is g.

In another possible implementation, the puncturing/shortening pattern isindicated by a sequence S, the puncturing pattern includes: successivelypuncturing the groups in a first order based on the sequence S; and theshortening pattern includes: successively shortening the groups in asecond order based on the sequence S, where the first order is frombeginning of the sequence S to the end of the sequence S or from the endof the sequence S to beginning of the sequence S, and the first orderand the second order are mutually reverse.

In another possible implementation, the puncturing/shortening pattern isindicated by a sequence S, and elements in the sequence S include groupnumbers of the g groups that are sorted based on the priority order ofpuncturing/shortening;

-   If g=4, S=[0, 1, 2, 3]; or    -   if g=8, S=[0, 1, 2, 4, 3, 5, 6, 7]; or    -   if g=16, S=[0, 1, 2, 4, 8, 3, 5, 9, 6, 10, 12, 7, 11, 13, 14,        15]; or    -   if g=32,    -   S=[0, 1, 2, 3, 4, 8, 16, 5, 6, 7, 9, 17, 10, 18, 11, 19, 12, 20,        13, 21, 14, 22, 24, 25, 26, 15, 23, 27, 28, 29, 30, 1]; or    -   if g=32,    -   S=[0, 1, 2, 3, 4, 8, 16, 5, 6, 7, 9, 17, 10, 18, 12, 20, 11, 19,        13, 21, 14, 22, 4, 25, 26, 15, 23, 27, 28, 29, 30, 31]; or    -   if g=64,    -   S=[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 16, 32, 17, 33, 12, 18, 34,        20, 36, 11, 13, 14, 15, 19, 35, 21, 37, 22, 38, 23, 39, 24, 40,        25, 41, 26, 42, 28, 44, 48, 49, 50, 52, 27, 43, 29, 45, 51, 30,        46, 31, 47, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63].

A bit position of a bit that needs to be punctured is determined inascending order of a natural order of the elements of the sequence S.The shortening pattern includes: determining, in descending order of anatural order of the elements of the sequence S, a bit position of a bitthat needs to be shortened.

In another possible implementation,

-   if g=4, the puncturing pattern is as follows: a group 0 is first    punctured, and then a first group and a second group are alternately    punctured; and the shortening pattern is as follows: a third group    is first shortened, and then a second group and a first group are    alternately shortened; or    -   if g=8, the puncturing pattern is as follows: a zeroth group is        first sequentially punctured and a first group, a second group        and a fourth group are alternately punctured, and then a sixth        group and a seventh group are alternately punctured; and the        shortening pattern is as follows: a seventh group and a sixth        group are first shortened, and then a fifth group and a third        group are alternately shortened; or    -   if g=16, the puncturing pattern is as follows: zeroth to second        groups are first sequentially punctured, a fourth group and an        eighth group are alternately punctured, a third group is        punctured, and then a fifth group and a ninth group are        alternately punctured; and the shortening pattern is as follows:        a 15^(th) group, a 14^(th) group; and a 13^(th) group are first        sequentially shortened, an 11^(th) group and a seventh group are        alternately shortened, a 12^(th) group is shortened, and then a        10^(th) group and a sixth group are alternately shortened; or    -   if g=32, the puncturing pattern is as follows: zeroth to fourth        groups are first sequentially punctured, an eighth group and a        16^(th) group are alternately punctured, a fifth group, a sixth        group, and a seventh group are sequentially punctured, a ninth        group and a 17^(th) group are alternately punctured, a 10^(th)        group and an 18^(th) group are alternately punctured, and then        an 11^(th) group and a 19^(th) group are alternately punctured;        and correspondingly, the shortening pattern is as follows: a        31^(st) group, a 30^(th) group, a 29^(th) group, a 28^(th)        group, and a 27^(th) group are first sequentially shortened, a        23^(rd) group and a 15^(th) group are alternately shortened; a        26^(th) group, a 25^(th) group, and a 24^(th) group are        sequentially shortened, a 22^(nd) group and a 14^(th) group are        alternately shortened, a 21^(st) group and a 13^(th) group are        alternately shortened, and then a 20^(th) group and a 12^(th)        group are alternately shortened; or if g=32, the puncturing        pattern is as follows: zeroth to fourth groups are first        sequentially punctured, an eighth group and a 16^(th) group are        alternately punctured, a fifth group, a sixth group, and a        seventh group are sequentially punctured, a ninth group and a        17^(th) group are alternately punctured, a 10^(th) group and an        18^(th) group are alternately punctured, and then a 12^(th)        group and a 20^(th) group are alternately punctured; and        correspondingly, the shortening pattern is as follows: a 31^(st)        group, a 30^(th) group, a 29^(th) group, a 28^(th) group, and a        27^(th) group are first sequentially shortened, a 23^(rd) group        and a 15^(th) group are alternately shortened, a 26th group, a        25th group, and a 24^(th) group are sequentially shortened, a        22^(nd) group and a 14^(th) group are alternately shortened, a        21^(st) group and a 13^(th) group are alternately shortened, and        then a 19^(th) group and an 11^(th) group are alternately        shortened; or    -   if g=64, the puncturing pattern is as follows: first        sequentially puncturing zeroth to 10^(th) groups are first        sequentially punctured, a 16^(th) group and a 32^(nd) group are        alternately punctured, a 17^(th) group and a 33^(rd) group are        alternately punctured, a 12^(th) group is punctured, a 18^(th)        group and a 34^(th) group are alternately punctured, a 20^(th)        group and a 36^(th) group are alternately punctured, an 11^(th)        group, a 13^(th) group, a 14^(th) group, and a 15^(th) group are        sequentially punctured, a 19^(th) group and a 35^(th) group are        alternately punctured, a 21^(st) group and a 37^(th) group are        alternately punctured, a 22^(nd) group and a 38^(th) group are        alternately punctured, and then a 23^(rd) group and a 39^(th)        group are alternately punctured; and the shortening pattern is        as follows: a 63^(rd) group, a 62^(nd) group, a 61^(st) group, a        60^(th) group, a 59^(th) group, a 58^(th) group, a 57^(th)        group, a 56^(th) group, a 55^(th) group, a 54^(th) group, and a        53^(rd) group are first sequentially shortened, a 47^(th) group        and a 31^(st) group are alternately shortened, a 46^(th) group        and a 30^(th) group are alternately shortened, a 51^(st) group        is shortened, a 45^(th) group and a 29^(th) group are        alternately shortened, a 43^(rd) group and a 27^(th) group are        alternately shortened, a 52^(nd) group, a 50^(th) group, a        49^(th) group, and a 48^(th) group are sequentially shortened, a        44^(th) group and a 28^(th) group are alternately shortened, a        42^(nd) group and a 26^(th) group are alternately shortened, a        41^(st) group and a 25^(th) group are alternately shortened, and        then a 40^(th) group and a 24^(th) group are alternately        shortened.

In another possible implementation, the puncturing/shortening pattern isindicated by a sequence S, and elements in the sequence S include groupnumbers of the g groups that are sorted based on the priority order ofpuncturing/shortening the g groups.

-   If g=4, S=[0, (1, 2), 3]; or    -   if g=8, S=[0, 1, (2, 4), (3, 5), 6, 7]; or    -   if g=16, S=[0, 1, 2, (4, 8), 3, (5, 9), (6, 10), 12, (7, 11),        13, 14, 15]; or-   if g=32,-   S=[0, 1, 2, 3, 4, (8, 16), 5, 6, 7, (9, 17), (10, 18), (11, 19),    (12, 20), (13, 21), (14, 22), 24, 25, 26, (15, 23), 27, 28, 29, 30,    31]; or-   if g=32,-   S=[0, 1, 2, 3, 4, (8, 16), 5, 6, 7, (9, 17), (10, 18), (12, 20),    (11, 19), (13, 21), (14, 22), 24, 25, 26, (15, 23), 27, 28, 29, 30,    31]; or-   if g=64,-   S=[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, (16, 32), (17, 33), 12, (18,    34), (20, 36), 11, 13, 14, 15, (19, 35), (21, 37), (22, 38), (23,    39), (24, 40), (25, 41), (26, 42), (28, 44), 48, 49, 50, 52, (27,    43), (29, 45), 51, (30, 46), (31, 47), 53, 54, 55, 56, 57, 58, 59,    60, 61, 62, 63]. Herein, ( ) used to indicate two groups with a same    priority, and coded bits in the two groups are alternately    punctured/shortened.

With reference to any one of the first to the sixth aspects, in apossible implementation, g is 4, 8, 16, 32, 64, 128, 256, 512, or 1024.

With reference to any one of the first to the sixth aspects, in apossible implementation, a group quantity g is determined by the lengthof mother code.

In a possible implementation, N/g is a fixed value; or when N is lessthan or equal to a preset value N0, g=g1; or when N is greater than N0,g=g2, where g1 and g2 are different values, and g1 and g2 each are oneof 4, 8, 16, 32, 64, 128, 256, 512, or 1024.

With reference to any one of the first to the sixth aspects, in apossible implementation, an order of puncturing/shortening inter-groupcoded bits is a natural order, a bit-reversal order, a reliabilityorder, or a code weight order.

With reference to any one of the first to the sixth aspects, in apossible implementation, rate matching is implemented by using a blockinterleaver: successively placing N coded bits into the blockinterleaver by column, where each column corresponds to one group;permuting columns of the block interleaver based on the determinedinter-group puncturing/shortening priority order, and permuting rows ofthe block interleaver based on an inner-group puncturing/shorteningorder; and when rate matching manner is a puncturing, sequentiallyreading M coded bits from a first start point of the block interleaver;or sequentially reading coded bits simultaneously from a first startpoint and a second start point of the block interleaver until M bits areobtained after combination; or when rate matching manner is ashortening, sequentially reading M coded bits from a third start pointof the block interleaver; or sequentially reading coded bitssimultaneously read from a third start, point and a fourth start pointof the block interleaver until M bits are obtained after combination,where N is a mother code length of a polar code, M is a target codelength, the first start point corresponds to a bit at a bit positionother than a punctured bit position, and the third start pointcorresponds to a bit at a bit position other than a shortened bitposition.

In a possible implementation, the first start point is a lower rightcorner of the block interleaver, the second start point is an endpointother than the first point on two ends of to-be-transmitted bits, thethird start point is an upper left corner of the block interleaver, andthe fourth start point is an endpoint other than the third point on twoends of to-be-transmitted bits.

In a possible implementation, when rate matching manner is puncturing,the M coded bits are sequentially read from the first start point of theblock interleaver.

With reference to any one of the first to the sixth aspects, in apossible implementation, when an actual code rate is greater than apreset threshold, rate matching manner is determined to use theshortening; or when an actual code rate is less than or equal to apreset threshold, rate matching manner is determined to use thepuncturing, where the actual code rate is K/M, K is a length ofinformation bits, and M is a length of target code.

In a possible implementation, a value range of the preset threshold is avalue within an interval [2/5, 1/2].

In a possible implementation, the preset threshold is 2/5, 4/9, or 1/2.

According to a seventh aspect, embodiments of this application provide acommunications apparatus, including a bus, a processor, a storagemedium, a bus interface, a network adapter, a user interface, and anantenna.

The bus is configured to connect the processor, the storage medium, thebus interface, and the user interface.

The processor is configured to perform the rate matching method in thefirst aspect or any implementation of the first aspect, or configured toperform the rate de-matching method in the fourth aspect or anyimplementation of the fourth aspect.

The storage medium is configured to store an operating system, andto-be-sent data or received data.

The bus interface is connected to the network adapter.

The network adapter is configured to implement a signal processingfunction of a physical layer in a wireless communications network.

The user interface is configured to connect to a user input device.

The antenna is configured to send and receive a signal.

Another aspect of this application provides a computer readable storagemedium. The computer readable storage medium stores an instruction. Whenthe instruction runs on a computer, the computer performs the method inany one of the foregoing aspects or implementations.

Another aspect of this application provides a computer program productincluding an instruction. When the instruction runs on a computer, thecomputer performs the method in any one of the foregoing aspects orimplementations.

Another aspect of this application provides a computer program. When thecomputer program runs on a computer, the computer performs the method inany one of the foregoing aspects or implementations.

In the embodiments of this application, the coded bits are divided intog groups, and group-based puncturing/shortening rate matching is easy toimplement, thereby improving polar code performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a basic wireless communication;

FIG. 2 is a schematic diagram of an application scenario of the datatransmission method according to an embodiment of this application;

FIG. 3 is a construction diagram of an Arikan polar code;

FIG. 4 is a schematic flowchart of a polar code rate matching methodaccording to an embodiment of this application;

FIG. 5 is a schematic diagram of dividing coded bits of a polar codeinto four groups for puncturing according to an embodiment of thisapplication;

FIG. 6 is a schematic diagram of dividing coded bits of a polar codeinto 32 groups for sequential puncturing according to an embodiment ofthis application;

FIG. 7 is a schematic diagram of implementing sequentialpuncturing/shortening by using a block interleaver according to anembodiment of this application;

FIG. 8 is a schematic diagram of reading coded bits in a blockinterleaver by column according to an embodiment of this application;

FIG. 9 is a schematic diagram of reading coded bits in a blockinterleaver by row according to an embodiment of this application;

FIG. 10 is a schematic diagram of a puncturing/shortening pattern of 32groups according to an embodiment of this application;

FIG. 11 is a schematic diagram of implementing sequential and alternatepuncturing/shortening by using an interleaver according to an embodimentof this application;

FIG. 12 shows a comparison between performance obtained by using asequential and alternate rate matching scheme when g=32 and performanceobtained by using the sequential and alternate rate matching scheme wheng=4 according to an embodiment of this application;

FIG. 13 is a schematic structural diagram of a rate matching apparatus1300 according to an embodiment of this application;

FIG. 14 is a schematic structural diagram of another e matchingapparatus 1400 according to this application;

FIG. 15 is a schematic flowchart of a polar code rate de-matching methodaccording to an embodiment of this application;

FIG. 16 is a schematic structural diagram of a rate de-matchingapparatus according to an embodiment of this application;

FIG. 17 is a schematic structural diagram of another rate de-matchingapparatus according to an embodiment of this application; and

FIG. 18 is a schematic structural diagram of a communications apparatusaccording to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

The following specific embodiments of this application with reference toaccompanying drawings.

FIG. 1 shows a basic procedure of wireless communication. Assuming thatcommunication signals are transmitted from a transmitting device(referred to as transmitting end hereinafter) to a receiving device(referred as receiving end hereinafter). At the transmitting end, asignal from a signal source is source encoded, channel encoded, ratematched, modulation mapped, and then transmitted to the receiving end.At the receiving end, after de-mapping demodulation, rate de-matching,channel decoding, and source decoding, the signal is output to a signaldestination. In channel encoding and channel decoding, the polar codingprocess as described above can be used. Because a code length of anoriginal polar code (mother code) is an integral power of 2, inpractical applications, the code length may need to be adjusted to adifferent code length. This can be achieved through rate matching. Atthe transmitting end, the rate matching is performed after the channelencoding, to achieve any target code length. At, the receiving end, arate de-matching is performed before channel decoding, to restore thepolar code to its original length.

The embodiments of this application may be applied to a wirelesscommunications system. The wireless communications system usuallyincludes multiple cells. Each cell includes at least one base station(BS). The base station provides a communications service for a pluralityof mobile stations MSs). The base station is connected to core networkequipment, as shown in FIG. 2 . The base station includes a basebandunit (BBU) and a remote radio unit (RRU). The BBU and the RRU may beplaced at different places. For example, the RRU is remote and placed ina heavy-traffic area, and the BBU is placed in a central equipment room.The BBU and the RRU may be alternatively placed in a same equipmentroom. The BBU and the RRU may alternatively be different components ofone rack.

Examples of wireless communications systems or schemes, in which theembodiments of this application may be applied, include but is notlimited to: a Narrowband Internet of Things (IB-IoT) system, a GlobalSystem for Mobile Communications (GSM), an Enhanced Data Rates for GSMEvolution (EDGE) system, a Wideband Code Division Multiple Access(WCDMA) system, a Code Division Multiple Access 2000 (CDMA2000) system,a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA)system, a Long Term Evolution (LTE) system, and three main applicationscenarios of the next-generation (5G) mobile communications system:enhanced mobile broadband (eMBB), ultra-Reliable and low-latencycommunication (URLLC), and enhanced Machine Type Communication (eMTC).

In the embodiments of this application, the base station is an apparatusthat is deployed in a radio access network and that provides a wirelesscommunications function for the MS. The base station may include a macrobase station, a micro base station (also referred to as a small cell), arelay station, an access point, and the like. In systems using differentradio access technologies, a device having a base station function mayhave different names. For example, the device may be referred to as anevolved NodeB, eNB or eNodeB) in the LTE system, a NodeB (in a 3rdGeneration (3G) system, or the like. For ease of description, in all theembodiments of this application, all the foregoing apparatuses thatprovide the wireless communications function for the MS are collectivelyreferred to as a network device, a base station, or a BS.

The MS in the embodiments of this application may include varioushandheld devices, in-vehicle devices, wearable devices, or a computingdevices that have a wireless communications function, or otherprocessing devices connected to a wireless modem. The MS may also bereferred to as a terminal and may further include a subscriber unit, acellular phone, a smartphone, a wireless data card, a personal digitalassistant (PDA) computer, a tablet computer, a wireless modem, ahandheld device, a laptop computer, a machine type communication (MTC)terminal, and the like. For ease of description, in all the embodimentsof this application, the foregoing mentioned devices are collectivelyreferred to as the MS.

A rate matching apparatus in the embodiments of this application may bethe BS or the MS mentioned above, an apparatus disposed in the BS or theMS, or an apparatus disposed in another wireless communications device.

Quasi-uniform puncturing (QUP) is one of coding and rate matchingmethods for implementing a polar code with any code length. A length ofmother code is first determined to be greater than or equal to anintegral power of 2. Then a puncturing pattern (bit position ofpuncturing) is determined based on the length of mother code and thelength of target code. The puncturing pattern may be represented byusing a binary sequence. “0” indicates the bit position of puncturing,and “1” indicates a bit position of non-puncturing. A channel capacitycorresponding to the bit position of puncturing is set to 0 (or an errorprobability is set to 1, or a signal-to-noise ratio SNR is set to beinfinitely small). Reliability of a polarized channel is calculated andsorted by using a density evolution method, a Gaussian approximationmethod, or a linear fitting method. A bit position of an information bit(including a check bit and an assistant bit) and a bit position of afrozen bit are determined. At receiving end, a bit need to be puncturedafter encoding to obtain the polar encoded bit sequence afterpuncturing.

Another method for polar code encoding and rate matching is shortening(or Shorten) a polar code. An encoded bit at a to-be-shortened locationis related only to a frozen bit. Reliability of a polarized channel isfirst calculated based on a mother code. Then one or more bit positionsof shortening is determined. One or more frozen bits are placed on acorresponding polarized channels. Then one or more bit positions forinformation bits (including a check bit and an assistant bit) and one ormore bit positions of frozen bits are determined from remainingpolarized channels based on the reliability. A bit placed at the bitposition for shortening after coding is deleted to obtain the polarcode, thereby implementing rate matching. In the shortening-based codingand rate matching scheme, the reliability of the polarized channel doesnot need to be recalculated (does not need to be reconstructed) based onthe bit position for shortening, and the frozen bit is placed on thepolarized channel corresponding to the to-be-shortened bit position,thereby greatly reducing polar code construction complexity. As shown inFIG. 3 , a coding matrix G_(N) is a lower triangular matrix, last (N−M)bits (N is a mother code length, and M is a target code length) may bedeleted, and frozen bits are placed on last (N−M) polarized channels. Inthis case, a to-be-punctured bit is related only to the frozen bit. Thismay be used as a feasible shortening pattern.

This application provides a polar code rate matching method. The methodis group-based puncturing/shortening. As shown in FIG. 4 , the ratematching method includes the following steps.

402. Obtain a first encoded bit sequence, where the first encoded bitsequence includes g groups that are of equal length, a quantity of firstencoded bits in each group is N/g, N is a length of mother code, N is anintegral power of 2, g is an integer greater than or equal to 4 and lessthan N, and g is an integral power of 2.

If g=4, the first encoded bits of the polar code are sequentiallydivided into four groups that are of equal length, and a quantity ofencoded bits in each group is N/4. For example, if the length of mothercode N is 64, and the first encoded bits are divided into four groups,the quantity of the first encoded bits in each group is 16; or if thelength of mother code N is 256, and the first encoded bits are dividedinto four groups, the quantity of the first encoded bits in each groupis 64. It can be learned that a larger value of N indicates a largerquantity of the first encoded bits in each group. A group granularity isrelatively large when the first encoded bits are divided into fourgroups. Therefore, to further improve performance, a grouping mannerwith a relatively small granularity may be used. For example, g is 8,16, 32, 64, 128, 256, 512, 1024, or the like, and g is an integral powerof 2. Certainly, g needs to be less than N, so that grouping ismeaningful.

A quantity of groups may be fixed, for example, 32. In this way, ratematching for any code length may be implemented by using a fixed blockinterleaver, a specific operation of the interleaver is determined by asequence S whose length is 32. In another design, it is ensured that aquantity of bits in each group is fixed, for example, 16. However, aquantity of groups increases with the mother code length. In otherwords, the quantity of groups is N/16. The quantity of groups may alsovary with the mother code length. For example, a larger mother codelength indicates a larger quantity of groups. In this way, a smallergranularity is designed for rate matching and a more flexible design mayindicate better performance. For example, a threshold N0 may be set.When N is less than or equal to the preset value N0, g=g1; and when N isgreater than N0, g=g2, where g1 and g2 are different values, and g1 andg2 each are one of 4, 8, 16, 32, 64, 128, 256, 512, or 1024. Forexample, N0=256, g1=8, and g2=32. A relationship between N and g mayalso be prestored in a table, and a quantity of groups obtained thoughdivision is determined by searching the table.

403. Determine, based on the groups, a bit position of a bit that needsto be punctured/shortened in the first encoded bit sequence.

Specifically, the bit position of the bit that needs to bepunctured/shortened in the first encoded bit sequence may be determinedbased on the groups and a puncturing/shortening pattern. Thepuncturing/shortening pattern determines a priority order ofpuncturing/shortening the g groups. A reverse relationship may existbetween the puncturing pattern and the shortening pattern. Bit positionsof bits that need to be punctured/shortened in all the groups may besuccessively determined based on the priority order ofpuncturing/shortening in all the groups. This pattern is brieflyreferred to as a sequential puncturing/shortening manner. A sequentialand alternate puncturing/shortening manner may be alternatively used. Tobe specific, bit positions of bits that need to be punctured/shortenedin a first quantity of groups are determined in the sequentialpuncturing/shortening manner based on a priority order, and an alternatepuncturing/shortening manner is used for encoded bits in groups with asame priority in a second quantity of groups. In other words, bits ingroups with different priorities are successively determined, based on apriority order of the groups, as bit positions of bits that need to bepunctured/shortened, and bits in different groups with a same priorityare successively determined, in the alternate manner, as bit positionsof bits that need to be punctured/shortened.

404. Obtain a second encoded bit sequence in the first encoded bitsequence after removing the bit that needs to be punctured/shortenedfrom the first encoded bit sequence, wherein the second encoded bitsequence is a bit sequence obtained after rate matching. In other words,a bit at a bit position specified by the puncturing/shortening patternmay be deleted, and a remaining encoded bit sequence is a bit sequenceobtained after rate matching.

Optionally, the rate matching method may further include a polar codingprocess:

-   -   placing a frozen bit on a polarized channel corresponding to the        bit position of the bit that needs to punctured/shortened; in        remaining polarized channels, selecting a polarized channel with        high reliability, placing an information bit (including a check        bit and an assistant bit) on the polarized channel with high        reliability, and placing frozen bits on the other polarized        channels; and encoding a to-be-coded bit by channel coding, to        obtain the first encoded bit sequence.

Optionally, the rate matching method may further include the followingstep:

401. Determine to use a shortening/puncturing rate matching manner.

Polar codes with different code lengths correspond to different QUPpuncturing patterns. Polarized channel reliability needs to berecalculated (needs to be reconstructed) based on a coding parametersuch as a code rate, and complexity is relatively high. For theshortening pattern, reliability of a later polarized channel in thepolar code is relatively high, and placing a frozen bit on the polarizedchannel may result in performance instability. Particularly, when a coderate is low, this may cause an extremely large performance loss.

Specifically, a puncturing/shortening method may be determined based onan actual code rate. A value of the actual code rate is compared with apreset threshold, to determine to perform puncturing/shortening ratematching. If the actual code rate R=K/M>R0, shortening rate matching isperformed. A coded bit at a to-be-shortened bit position is shortened(deleted), and a frozen bit is placed on a polarized channel whosesequence number is equal to that of the to-be-shortened bit position.During decoding, a log-likelihood ratio LLR of the shortened bitposition is set to be infinitely large. If the actual code rate R≥R0,puncturing rate matching is performed. A coded bit at a to-be-puncturedbit position is punctured (deleted), and a frozen bit is placed on apolarized channel whose sequence number is equal to that of theto-be-punctured bit position. During decoding, an LLR of the puncturedbit position is set to 0. The value of the preset threshold R0 may bebetween 2/5 and 1/2, for example, the value of R0 is 2/5, 4/9, 1/2, orthe like.

The puncturing pattern or the shortening pattern in this embodiment ofthis application indicates an order that is used to determine a groupthat is first punctured/shortened and a group that ispunctured/shortened later during puncturing/shortening. A priority orderspecified in the puncturing pattern or the shortening pattern may beused to determine a bit position of a to-be-punctured or to-be-shortenedcoded bit. A reverse relationship may exist between the designedpuncturing pattern and shortening pattern. For coding bits, puncturingis performed from the front beginning to the end, and shortening isperformed from the end to the beginning.

The puncturing/shortening pattern may be indicated by using a sequenceS, and group numbers of the g groups are ordered based on a priorityorder of puncturing/shortening the g groups. Elements of the sequence Sinclude group numbers of the g groups sorted based on the priority orderof puncturing/shortening the g groups. The indication sequence S may bea reliability sequence, a natural order sequence, a code weight ordersequence of the polar code, or another sequence with excellentperformance. The puncturing pattern includes: successively puncturingthe groups in a first order based on the sequence S. The shorteningpattern includes: successively shortening the groups in a second orderbased on the sequence S. The first order is from the beginning to theend or from the end to the beginning, and the first order and the secondorder are mutually reverse.

For example, g=32, and a sequence that is obtained after polarizedchannels of the polar code whose mother code length is 32 are sortedbased on reliability may be used as an indication sequence. In anexample, a sequence that is obtained after reliability calculated basedon a polarization weight is sorted in ascending order is as follows:

-   -   S=[0, 1, 2, 4, 8, 16, 3, 5, 6, 9, 10, 17, 12, 18, 20, 24, 7, 11,        13, 19, 14, 21, 22, 25, 26, 28, 15, 23, 27, 29, 30, 31].

In another example, a sequence that is obtained after reliabilitycalculated based on a Gaussian approximation (GA) or density evolution(DE) method is sorted in ascending order is as follows:

-   -   S=[0, 1, 2, 4, 8, 16, 3, 5, 6, 9, 10, 17, 12, 18, 20, 7, 24, 11,        13, 19, 14, 21, 22, 25, 26, 28, 15, 23, 27, 29, 30, 31].

In still another example, a quantity of 1s in a row of a coding matrixof the polar code is a code weight of the row. Sorting is performed inascending order based on the code weight. A smaller sequence number insequence numbers with a same code weight is placed at the front.Therefore, a sequence of sorting code weights is obtained. The sequenceof sorting the code weights in ascending order is as follows:

-   -   S=[0, 1, 2, 4, 8, 16, 3, 5, 6, 9, 10, 12, 17, 18, 20, 24, 7, 11,        13, 14, 19, 21, 22, 25, 26, 28, 15, 23, 27, 29, 30, 31].

For an indication sequence when another value of g is used, acorresponding reliability sequence, a natural order sequence, a codeweight order sequence of the polar code may be obtained with referenceto the manner used when g=32. Puncturing is performed from the beginningto end based on the indication sequence S. To be specific, puncturing isperformed from a group indicated by a first element of the sequence, andis further performed on a group indicated by a second element if aquantity of punctured bits is less than a quantity of bits that need tobe punctured. Sequential puncturing is performed until the quantity ofbits that need to be punctured are punctured. Shortening is performedfrom back to front. To be specific, shortening is performed from a groupindicated by a last element of the sequence S, and is further performedon a group indicated by a penultimate element if a quantity of shortenedbits is less than a quantity of bits that need to be shortened.Sequential shortening is performed until the quantity of bits that needto be shortened are shortened. In the puncturing/shortening process, ifa quantity of remaining bits that need to be punctured/shortened is lessthan a total quantity of bits in one group, for an inner-grouppuncturing/shortening order, refer to an inter-grouppuncturing/shortening order. In other words, the inner-grouppuncturing/shortening order may be a reliability sequence, a naturalorder sequence, a code weight order sequence of the polar code, oranother sequence with excellent performance. It is assumed that themother code length N=256, and g″32. A quantity of bits in each group is256/32=8. The 8 bits in each group may be sorted based on a reliabilitysequence used when N=8, in a natural order, or based on a code weightorder used when N=8. For the puncturing/shortening order, refer to theinter-group puncturing/shortening order described above.

There may be two group-based puncturing/shortening manners. One manneris natural-order puncturing/shortening. Bit positions of bits that needto be punctured/shortened in all groups obtained through division aresuccessively determined based on a priority order that is ofpuncturing/shortening all the groups and that is determined based on apuncturing/shortening pattern. Another manner is natural-order andalternate puncturing/shortening. A puncturing/shortening patternincludes: successively determining, based on a group priority order,bits in a first quantity of groups as bit positions of bits that need tobe punctured/shortened, and successively determining, in an alternatemanner, bits in different groups with a same priority in a secondquantity of groups as bit positions of bits that need to bepunctured/shortened. The following describes the two manners withreference to a coding and rate matching process.

(1) Sequential Puncturing/Shortening Encoding and Rate Matching Scheme.

Encoded bits of a polar code are sequentially divided into severalgroups that are of equal length. Puncturing/shortening is performed in aunit of group (based on groups) based on a puncturing/shortening patternindicated by a specific sequence S. A length of S is the same as aquantity of groups of S. All bits in a group specified by an element arepunctured/shortened based on an element order of S. If a quantity ofremaining bits that need to be punctured/shortened exceeds a quantity ofbits in one group, all bits in a group specified by a next element arepunctured/shortened; or if a quantity of remaining bits that need to bepunctured/shortened is less than a quantity of bits in one group, a bitin the group is punctured/shortened based on another specific order. Adetermined to-be-punctured/shortened bit position indicates that thepuncturing/shortening pattern is determined. A frozen bit is placed on apolarized channel corresponding to a sequence number of ato-be-punctured/shortened bit. In remaining polarized channels, apolarized channel with high reliability is selected, an information bit(including a check bit and an assistant bit) is placed on the polarizedchannel with high reliability, and frozen bits are placed on the otherpolarized channels. A to-be-coded bit is mapped to the information bitfor channel coding, and a coded bit at a bit position specified by thepuncturing/shortening pattern is deleted to obtain a coded bit obtainedafter rate matching. Whether to select a puncturing rate matching methodor a shortening rate matching method may be determined based on a coderate. To be specific, the shortening rate matching method is selectedwhen the code rate exceeds a preset threshold; or the puncturing ratematching method is selected when the code rate does not exceed a presetthreshold.

(2) Coding and Rate Matching Scheme in Which Natural-OrderPuncturing/shortening and Alternate Puncturing/Shortening Are Combined.

In this scheme, in groups indicated by all elements of an indicationsequence, puncturing/shortening is successively performed in the naturalorder on some groups, and inter-group alternate puncturing/shortening isperformed on some inter-group coded bits. To be specific, the puncturingpattern is set as follows: puncturing a first quantity of groups basedon a priority order, and puncturing groups with a same priority in asecond quantity of groups in an alternate order. Correspondingly, theshortening pattern is set as follows: shortening a first quantity ofgroups based on a priority order, and shortening groups with a samepriority in a second quantity of groups in an alternate manner.

For example, g=4. As shown in FIG. 5 , the coded bits of the polar codeare divided into four groups: B0, B1, B2, and B3 in the natural order.During puncturing, the first group B0 is first sequentially punctured ina front-to-back order. If a quantity of to-be-punctured bits exceeds aquantity of coded bits in one group, after all coded bits in the firstgroup are punctured, the two middle segments B1 and B2 are alternatelypunctured in a front-to-back order until a required code length isreached. A to-be-shortened bit position is opposite to a to-be-puncturedbit position. The last group B3 is first shortened, and then the twomiddle group are alternately shortened in a back-to-front order. Wheng=4, performance obtained in some area in which a puncturing order inthe sequential and alternate scheme is used may be approximate toperformance obtained through reconstruction. However, when a quantity ofto-be-punctured bits is approximately ¼ mother code length, there is anobvious performance loss relative to performance obtained throughpuncturing based on reliability. If g is greater than 4, for example, gis 16, 32, 64, or larger, for a priority order of puncturing/shorteninggroups, refer to a sequential and alternate principle used when fourgroups are obtained through division. For example, first N/4 coded bitsare sequentially punctured/shortened, middle N/2 coded bits arealternately punctured/shortened, and last N/4 bits are sequentiallypunctured/shortened. Certainly, a quantity of coded bits that need to bepunctured/shortened usually does not exceed N/2 because if the quantityexceeds N/2, a smaller mother code length may be used during coding.Therefore, if puncturing is performed from front to back, and shorteningis performed in a back-to-front order, the first N/4 coded bits are onlypunctured and are not shortened, the middle N/2 coded bits may bepunctured/shortened, and the last N/4 coded bits are only shortened. Inother words, if puncturing is performed from front to back, andshortening is performed in a back-to-front order, first g/4 groups areonly punctured and are not shortened, middle g/2 groups may bepunctured/shortened, and last g/4 groups are only shortened.

To further improve performance, the group granularity is changed, or thepuncturing/shortening pattern (the sequence S) is optimized. Inaddition, to facilitate implementation and improve performancestability, a symmetrical sequence S may be used. To be specific, grouppositions in the sequence S are symmetrical based on a group sortingresult. In other words, positions of first g/2 groups are symmetrical topositions of last g/2 groups in the sequence S. The following lists somesymmetrical sequences S that may be applied to a sequentialpuncturing/shortening case. In the sequence, bold group numbers indicatefirst g/2 groups, and non-bold group numbers indicate last g″2 groups. Abold type is only for ease of description, and whether a sequence numberis bold does not indicate a sequence difference.

-   If g=4, S=[0, 1, 2, 3].    -   if g=8, S=[0, 1, 2, 4, 3, 5, 6, 7].    -   if g=16, S=[0, 1, 2, 4, 8, 3, 5, 9, 6, 10, 12, 7, 11, 13, 14,        15].    -   if g=32,    -   S=[0, 1, 2, 3, 4, 8, 16, 5, 6, 7, 9, 17, 10, 18, 11, 19, 12, 20,        13, 21, 14, 22, 24, 25, 26, 15, 23, 27, 28, 29, 30, 1].    -   if g=32, the sequence S may be further adjusted to:    -   S=[0, 1, 2, 3, 4, 8, 16, 5, 6, 7, 9, 17, 10, 18, 12, 20, 11, 19,        13, 21, 14, 22, 4, 25, 26, 15, 23, 27, 28, 29, 30, 31].    -   if g=64,    -   S=[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 16, 32, 17, 33, 12, 18, 34,        20, 36, 11, 13, 14, 15, 19, 35, 21, 37, 22, 38, 23, 39, 24, 40,        25, 41, 26, 42, 28, 44, 48, 49, 50, 52, 27, 43, 29, 45, 51, 30,        46, 31, 47, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63].

A bit position of a bit that needs to be punctured is determined inascending order of a natural order of elements of the sequence S. Ashortening pattern includes: determining, in descending order of anatural order of elements of the sequence S, a bit position of a bitthat needs to be shortened.

If the symmetrical sequence S is sequentially and alternatelypunctured/shortened, a group order is unchanged. However, duringalternate puncturing/shortening, an alternately group need to bepunctured/shortened may be identified by using brackets, to indicatethat different groups indicated in the brackets have a same priority,and bits in different groups are alternately punctured/shortened.Therefore, the symmetrical sequence S may be represented as follows:

If g=4, S=[0, (1, 2), 3]; or a puncturing/shortening pattern isrepresented as follows: for the puncturing pattern, first puncturing azeroth group, and then alternately puncturing a first group and a secondgroup; and for the shortening pattern, first shortening a third group,and then alternately shortening a second group and a first group.

If g=8, S=[0, 1, (2, 4), (3, 5), 6, 7]; or a puncturing/shorteningpattern is represented as follows: for the puncturing pattern,sequentially puncturing a zeroth group and a first group, and thenalternately puncturing a second group and a fourth group; and for theshortening pattern, first shortening a seventh group and a sixth group,and then alternately shortening a fifth group and a third group.

If g=16,

S=[0, 1, 2, (4, 8), 3, (5, 9), (6, 10), 12, (7, 11), 13, 14, 15]; or apuncturing/shortening pattern is represented as follows: for thepuncturing pattern, first sequentially puncturing zeroth to secondgroups, alternately puncturing a fourth group and an eighth group,puncturing a third group, and then alternately puncturing a fifth groupand a ninth group; and for the shortening pattern, sequentiallyshortening a 15^(th) group, a 14^(th) group; and a 13^(th) groupalternately shortening an 11^(th) group and a seventh group, shorteninga 12^(th) group, and then alternately shortening a 10^(th) group and asixth group.

If g=32,

-   -   S=[0, 1, 2, 3, 4, (8, 16), 5, 6, 7, (9, 17), (10, 18), (11, 19),        (12, 20), (13, 21), (14, 22), 24, 25, 26, (15, 23), 27, 28, 29,        30, 31].

For ease of expression, S may also be represented as follows:

-   -   S=[0, 1, 2, 3, 4, (8, 16), 5, 6, 7, (9-11, 17-19), (12-14,        20-22), 24, 25, 26, (15, 23), 27, 28, 29, 30, 31]; or    -   a puncturing/shortening pattern is represented as follows: for        the puncturing pattern, first sequentially puncturing zeroth to        fourth groups, alternately puncturing an eighth group and a        16^(th) group, sequentially puncturing a fifth group, a sixth        group, and a seventh group, alternately puncturing a ninth group        and a 17^(th) group, alternately puncturing a 10^(th) group and        an 18^(th) group, and then alternately puncturing an 11^(th)        group and a 19^(th) group; and for the shortening pattern, first        sequentially shortening a 31^(st) group, a 30^(th) group, a        29^(th) group, a 28^(th) group, and a 27^(th) group, alternately        shortening a 23^(rd) group and a 15^(th) group, sequentially        shortening a 26^(th) group, a 25^(th) group, and a 24^(th)        group, alternately shortening a 22^(nd) group and a 14^(th)        group, alternately shortening a 21^(st) group and a 13^(th)        group, and then alternately shortening a 20^(th) group and a        12^(th) group.

Alternatively, if g=32,

-   -   S=[0, 1, 2, 3, 4, (8, 16), 5, 6, 7, (9, 17), (10, 18), (12, 20),        (11, 19), (13, 21), (14, 22), 24, 25, 26, (15, 23), 27, 28, 29,        30, 31]; or    -   a puncturing/shortening pattern is represented as follows: for        the puncturing pattern, first sequentially puncturing zeroth to        fourth groups, alternately puncturing an eighth group and a        16^(th) group, sequentially puncturing a fifth group, a sixth        group, and a seventh group, alternately puncturing a ninth group        and a 17th group, alternately puncturing a 10^(th) group and an        18^(th) group, and then alternately puncturing a 12^(th) group        and a 20^(th) group; and for the shortening pattern, first        sequentially shortening a 31^(st) group, a 30^(th) group, a        29^(th) group, a 28^(th) group, and a 27^(th) group, alternately        shortening a 23^(rd) group and a 15^(th) group, sequentially        shortening a 26th group, a 25^(th) group, and a 24^(th) group,        alternately shortening a 22^(nd) group and a 14^(th) group,        alternately shortening a 21^(st) group and a 13^(th) group, and        then alternately shortening a 19^(th) group and an 11^(th)        group.

If g=64,

-   -   S=[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, (16, 32), (17, 33), 12,        (18, 34), (20, 36), 11, 13, 14, 15, (19, 35), (21, 37), (22,        38), (23, 39), (24, 40), (25, 41), (26, 42), (28, 44), 48, 49,        50, 52, (27, 43), (29, 45), 51, (30, 46), (31, 47), 53, 54, 55,        56, 57, 58, 59, 60, 61, 62, 63]; or    -   a puncturing and shortening pattern is represented as follows:        for the puncturing pattern, first sequentially puncturing zeroth        to 10^(th) groups, alternately puncturing a 16^(th) group and a        32^(nd) group, alternately puncturing a 17^(th) group and a        33^(rd) group, puncturing a 12^(th) group, alternately        puncturing a 12^(th) group and a 34^(th) group, alternately        puncturing a 20^(th) group and a 36^(th) group, sequentially        puncturing an 11^(th) group, a 13^(th) group, a 14^(th) group,        and a 15^(th) group, alternately puncturing a 19^(th) group and        a 35^(th) group, alternately puncturing a 21^(st) group and a        37^(th) group, alternately puncturing a 22^(nd) group and a        38^(th) group, and then alternately puncturing a 23^(rd) group        and a 39^(th) group; and for the shortening pattern,        sequentially shortening a 63^(rd) group, a 62^(nd) group, a        61^(st) group; a 60^(th) group; a 59^(th) group, a 58^(th)        group, a 57^(th) group, a 56^(th) group, a 55^(th) group, a        54^(th) group, and a 53^(rd) group, alternately shortening a        47^(th) group and a 31^(st) group, alternately shortening a        46^(th) group and a 30^(th) group, shortening a 51^(st) group,        alternately shortening a 45^(th) group and a 29^(th) group,        alternately shortening a 43^(rd) group and a 27^(th) group,        sequentially shortening a 52^(nd) group, a 50^(th) group, a        49^(th) group, and a 48^(th) group, alternately shortening a        44^(th) group and a 28^(th) group, alternately shortening a        42^(th) group and a 26^(th) group, alternately shortening a        41^(st) group and a 25^(th) group, and then alternately        shortening a 40^(th) group and a 24^(th) group.

In the foregoing sequences, two groups in brackets have a same priority,and are alternately punctured/shortened, and groups outside brackets arepunctured/shortened based on a natural order of the sequence S. Apriority order of determining to-be-punctured bit positions is abegin-to-end order of the sequence S, and a priority order ofdetermining to-be-shortened bit positions is a begin-to-end order of thesequence S (wherein “begin-to-end order” is an order from the beginningof the bit sequence to end of the bit sequence).

The puncturing/shortening pattern described in this applicationindicates a priority order of puncturing/shortening all groups. Thisdoes not mean that all groups indicated by the puncturing/shorteningpattern are punctured/shortened. Instead, a coded bit that needs to bepunctured/shortened is determined based on the puncturing/shorteningpattern and a quantity of coded bits that need to bepunctured/shortened, until the quantity of coded bits that need to bepunctured/shortened is determined. A remaining coded bit that is notdetermined as a coded bit that needs to be punctured/shortened is acoded bit obtained after rate matching, and is to be transmitted to areceive end.

With reference to a coding and rate matching process, the followingdescribes application of the rate matching method provided in thisapplication. For a polar code in which a mother code length is N, atarget code length is M (when M<N, puncturing/shortening rate matchingneeds to be implemented; or if M≥N, repetition or segmentation ratematching may be implemented), and a length of information bits(including a check bit and a assistant bit) is K, a coding and ratematching process may include: selecting (N−M) coded bits from the mothercode as to-be-punctured/shortened bits based on a puncturing/shorteningpattern, placing a frozen bit on a polarized channel with a sequencenumber corresponding to the (N−M) coded bits need to bepunctured/shortened; in remaining polarized channels after the codedbits to be punctured/shortened are selected, selecting a polarizedchannel with high reliability, placing an information bit (including acheck bit and a assistant bit) on the polarized channel with highreliability, and placing frozen bits on the other channels; mapping theinformation bit (including a check bit and a assistant bit) to theinformation bit for channel coding; and puncturing a bit positionspecified by the puncturing/shortening pattern, to obtain a encoded bitobtained after rate matching. Whether to use a puncturing rate matchingmanner or a shortening rate matching manner and whether to use apuncturing pattern or a shortening pattern are determined in theforegoing described manners.

The following uses an example in which g=32, to describe a method forsequentially determining a to-be-punctured/shortened bit position.Whether to use a puncturing rate matching method or a shortening ratematching method is determined. Coded bits of a polar code aresequentially divided into 32 equal-length groups, and a quantity ofcoded bits in each group is N/32. A to-be-punctured/shortened bitposition is determined in a unit of group based on a sequence S (whoselength is 32). When a quantity of to-be-punctured/shortened bits is P, aquantity of groups that need to be completely deleted isnumG=floor(P/(N/32)), and a quantity of to-be-punctured bits in aremaining group that does not need to be completely deleted isP−numG*N/32, where floor indicates rounding down. That the quantity ofgroups that need to be completely deleted is numG indicates that allgroups specified by first numG elements of the sequence S are to bepunctured/shortened. That the group does not need to be completelypunctured/shortened indicates that remaining N−M−numG*N/32to-be-punctured/shortened bits are selected from a group specified by a(numG+1)^(th) element of the sequence S. An information bit is mapped toan information bit channel, and is coded based on a coding matrixG_(N)=F₂ ^(⊗(log) ² ^((N))). A coded bit at the determinedto-be-punctured/shortened bit position is deleted when a coded bitsequence obtained after rate matching is sent.

Assuming that g=32, a corresponding sequence is as follows:

-   -   S=[0, 1, 2, 3, 4, 8, 16, 5, 6, 7, 9, 17, 10, 18, 11, 19, 12, 20,        13, 21, 14, 22, 24, 25, 26, 15, 23, 27, 28, 29, 30, 31].

The sequence indicates a number of a to-be-punctured group from front toback. In other words, a puncturing priority is as follows: firstpuncturing a zeroth group, and then successively puncturing a firstgroup, a second group, a third group, and on the like until a puncturingquantity reaches a required puncturing quantity. In other words, thezeroth group has a first priority to be punctured, the first group has asecond priority, and a 19^(th) group has a 16^(th) priority.

A puncturing order generated by the sequence is shown in FIG. 6 . In thefigure, a number at a right side is a group sequence number, and a grayblock is a candidate to-be-punctured bit. A number in the gray block isa priority order of puncturing groups, and a smaller number indicates ahigher puncturing priority.

Front and back locations of S are symmetrical, and a reversed S from thebeginning to the end is a shortening indication sequence. For example, agroup 0 indicated by a first element in the S is symmetrical to a group31 indicated by a last element in the 5, and a group 1 indicated by asecond element in the S is also symmetrical to a group 30 indicated by apenultimate element in the S. The sequence indicates a number of ato-be-shortened group from the end to the beginning. In other words, ashortening priority is as follows: first shortening a 31^(st) group, andthen successively shortening a 30^(th) group, a 29^(th) group, and thelike until a shortening quantity reaches a required shortening quantity.In other words, the 31^(st) group has a first priority to be shortened,the 30^(th) group has a second priority, and a 12^(th) group has a16^(th) priority.

In a sequential puncturing/shortening scheme, rate matching may beimplemented by using a block interleaver. N coded bits are successivelyplaced into the block interleaver by column. Each column corresponds toone group, and there are g columns and N/g rows in total. Columns of theblock interleaver are permuted based on a determined inter-grouppuncturing/shortening priority order, and rows of the block interleaverare permuted based on an inner-group puncturing/shortening order. If itis determined to use a puncturing rate matching manner, M coded bits aresequentially read from a first start point of the block interleaver; orcoded bits are sequentially read simultaneously from a first start pointand a second start point of the block interleaver until M bits areobtained after combination. If it is determined to use a shortening ratematching manner, M coded bits are sequentially read from a third startpoint of the block interleaver; or coded bits are sequentially readsimultaneously from a third start point and a fourth start point of theblock interleaver until M bits are obtained after combination. N is amother code length of a polar code, M is a target code length, the firststart point corresponds to a bit at a bit position except a puncturedbit position, and the second start point corresponds to a bit at a bitposition except a shortened bit position.

The following uses an example in which g=32, to describe a method forimplementing rate matching by using the block interleaver. Animplementation process of the block interleaver includes: writing Ncoded bits into the block interleaver by column, where the blockinterleaver includes 32 columns and N/32 rows in total; first performingcolumn permutation based on a sequence S, in other words, groups arerearranged; then performing row permutation based on the inner-grouppuncturing/shortening order, in other words, rearranging an inner-groupbit order; and gathering to-be-punctured/shortened bits on an end of theblock interleaver after the column permutation and the row permutation.As shown in FIG. 7 , if puncturing is to be performed, to-be-punctured(to-be-deleted) bits are gathered on a leftmost side (a grey area) ofthe block interleaver; if shortening is to be performed, to-be-deletedbits are gathered on a rightmost side (a grid area) of the blockinterleaver.

Because the to-be-deleted bits have been gathered together, interleavingmay be differently implemented by adjusting an order of readingto-be-transmitted bits, to meet a requirement of higher order modulationand a fading channel. For example, the to-be-transmitted bits aredirectly sequentially read. During shortening, reading is started froman upper left corner of the block interleaver, in other words, readingis sequentially performed from a first element downwards by column untilM coded bits are read. During puncturing, reading is started from alower right corner of the block interleaver, in other words, reading issequentially performed from a last element upwards by column until Mcoded bits are read. During repetition, reading may be performed in anyorder. To be specific, the block interleaver also provides a repetitionpattern, namely, a coded bit selection order during repetition. Becausebit positions of the to-be-transmitted bits may be conveniently obtainedthrough calculation, alternatively, reading may be sequentiallyperformed simultaneously from two ends of the to-be-transmitted bits,and read bit streams are finally directly connected. In FIG. 7 , thefirst start point is a bit position indicated by 701 at a lower rightcorner, the second start point is a bit position indicated by 702, thethird start point is a bit position indicated by 703 at an upper leftcorner, and the fourth start point is a bit position indicated by 704.

After a column is read, cyclic shift may be further performed on thecolumn. A cyclic shift value of each column may be determined based on afunction, for example, 5*i, or ƒ₁*i+ƒ₂*i², or ┌(ƒ₁*i+ƒ₂*i²)/a┐ where ┌·┐indicates rounding up, i is a column number, and f₁, f₂, and a areconstants. Cyclic shift of each column is ensured as much as possible tobe random. In this way, a final read coded sequence is broken afterinterleaving, so that relatively good performance can be achieved in acase of the higher order modulation and the fading channel.

A reading manner of the block interleaver may also be manners shown inFIG. 8 and FIG. 9 . Reading is performed by column in FIG. 8 , andreading is performed by row in FIG. 9 . FIG. 8 and FIG. 9 use an exampleof shortening, and puncturing is similar. In a process of performingreading by column in FIG. 8 , a column reading order is reversed every Lcolumns. For example, column reading is first performed from top tobottom, and then column reading is performed from bottom to top. Herein,L may be a constant; or L may be related to a modulation order. Forexample, when the modulation order is 16 QAM, L may be 3, 5, or thelike; when the modulation order is 64 QAM, L is 5, 6, 32, or the like.When L is the same as a quantity of columns, the reading order is notchanged. In a process of performing reading by row in FIG. 9 , rowreading may be directly performed from left to right, or may beperformed in a manner similar to the manner of performing reading bycolumn. A reading order is reversed every several rows, in other words,reading is performed from right to left.

The following uses an example in which g=32, to describe a method forsequentially and alternately determining a puncturing/shortening patternwhen 32 groups are obtained through division. Whether rate matching isperformed by using a puncturing rate matching manner or a shorteningrate matching manner is determined. Coded bits of a polar code aresequentially divided into 32 equal-length groups, and a quantity ofcoded bits in each group is N/32. A to-be-punctured/shortened bitposition is determined in a unit of group based on a sequence S (whoselength is 32). If a current element is one number, a group indicated bythe element is punctured, and an inner-group puncturing order may be thesame as the order described above. If a current element is two or morenumbers in brackets, groups indicated by the numbers are alternatelypunctured, and an inner-group puncturing order may be the same as theorder described above.

It is assumed that a sequence S whose length is 32 is as follows:

-   -   S=[0, 1, 2, 3, 4, (8, 16), 5, 6, 7, (9, 17), (10, 18), (11, 19),        (12, 20), (13, 21), (14, 22), 24, 25, 26, (15, 23), 27, 28, 29,        30, 31].

The sequence indicates a number of a to-be-punctured group from front toback. In other words, a zeroth group is first punctured, and then afirst group, a second group, and the like are successively punctured.After a fourth group is punctured, an eighth group and a 16^(th) groupare alternately punctured, and then a fifth group is punctured. Thesequence S indicates a number of a to-be-shortened group from back tofront. In other words, a 31^(st) group is first shortened, and then a30^(th) group, a 29^(th) group, and the like are shortened. S issymmetrical, and a reversed S is a shortening indication sequence fromfront to back.

A puncturing order generated by the sequence is shown in FIG. 10 . Inthe figure, a number at a right side is a group sequence number, and anarea with lines is a candidate to-be-punctured bit. A number is apriority order of puncturing groups. An area with a smaller number isdeleted earlier, and areas with a same number are alternately punctured.An inner-group puncturing/shortening order of bits may be a naturalorder. The puncturing order is a front-to-back order, and the shorteningorder is a back-to-front order. Alternatively, an inner-grouppuncturing/shortening order of bits may be an inner-group reliabilityorder. To be specific, puncturing may be performed in ascending order ofreliability, and shortening may be performed in descending order ofreliability.

In FIG. 10 , when a quantity of groups that need to be punctured is lessthan or equal to 5, a zeroth group to a fourth group are firstsequentially punctured; when a quantity of groups that need to bepunctured is six to seven, an eighth group and a 16^(th) group arealternately punctured after a zeroth group to a fourth group arepunctured; when a quantity of groups that need to be punctured is eightto ten, a fifth group to a seventh group are sequentially puncturedafter the foregoing groups are punctured; when a quantity of segmentsthat need to be punctured is greater than or equal to 11, alternatepuncturing is successively performed on a ninth group and a 17^(th)group, a 10^(th) group and an 18^(th) group, and an 11^(th) group and a19^(th) group after the foregoing groups are punctured. The three pairs(9, 17), (10, 18), and (11, 19) are closely adjacent, and therefore mayalso be represented as (9-11, 17-19). In other words, ninth to 11^(th)groups and 17^(th) to 19^(th) groups are alternately punctured. Ato-be-punctured bit position indicated by the sequence may be determinedby using a pseudo code in the following, where q indicates whether a bitis to be punctured. If q at a current bit position is 1, it indicatesthat the bit is to be punctured; otherwise, it indicates that a bit atthe current bit position is not to be punctured.

If P≤N*5/32% sequentially puncturing zeroth to fourth groups

-   -   q(1:P)=% zeroth to fourth groups    -   else if P≤N*7/32% alternately puncturing an eighth group and a        16^(th) group    -   q(1:N*5/32)=1;    -   q(N/4+(1:ceil((P−N*5/32)/2)))=1; % eighth group    -   q(N/2+(1:floor((P−N*5/32)/2)))=1; % 16^(th) group    -   else if P≤N0*5/16% sequentially puncturing fifth to seventh        segments    -   q(1:N*5/32)=1;    -   q(N/4+(1:N/32))=1;    -   q(N/2+(1:N/32))=1;    -   q(N*5/32+(1:P−N*7/32))=1; % fifth to seventh groups    -   Else % alternately puncturing ninth segment and a 17^(th)        segment    -   q(1:N/4)=1;    -   q(N/4+(1:ceil((P−N/4)/2)))=1; % ninth to 11^(th) groups    -   q(N/2+(1:floor((P−N/4)/2)))=1; % 17^(th) to 19^(th) groups    -   end

In FIG. 10 , a case of shortening is contrary to that of puncturing.When a quantity groups that need to be shortened is less than or equalto 5, a 31^(st) group, a 30^(th) group, a 29^(th) group, and a 27^(th)group (for ease of description, the consecutive groups in a reversedorder may be represented as 31^(st) to 27^(th) groups) are firstsequentially shortened. When a quantity groups that need to be shortenedis 6 to 7, a 23^(rd) group and a 15^(th) group are alternately shortenedafter the 31^(st) to 27^(th) groups are shortened. When a quantitygroups that need to be shortened is 8 to 10, 26^(th) to 24^(th) groupsare sequentially shortened after the foregoing groups are shortened.When a quantity segments that need to be shortened is greater than orequal to 11, alternate shortening is successively performed on a 22^(nd)group and a 14^(th) group, a 21^(st) group and a 13^(th) group, and a20^(th) group and a 12^(th) group after the foregoing groups areshortened. The three pairs (12, 20), (13, 21), (14, 22) are closelyadjacent, and therefore may also be represented as (22-20, 14-12). Inother words, 22^(nd) to 20^(th) groups and 14^(th) to 12^(th) groups arealternately shortened.

As shown in FIG. 11 , sequential and alternate rate matching may beimplemented by using an interleaver. For example, g=32. Specificimplementation of the interleave is as follows: sequentially placingfirst 1/4: zeroth to seventh groups of N coded bits and last 1/4:24^(th) to 31^(st) groups of the N coded bits; two middle (1/4)s: eighthto 15^(nd) groups and 16^(th) to 23^(rd) groups of the N coded bits arealternately placed. Then, group permutation is performed based on thesequence S, to rearrange a group order. After the coded bits areinterleaved, if puncturing is to be performed, to-be-punctured bits aregathered at an upmost side of the interleaver; if shortening is to beperformed, to-be-shortened bits are gathered at a downmost side of theinterleaver. Repetition may be implemented by performing cyclic readingon bits in the interleaver.

FIG. 12 shows a comparison between performance obtained by using asequential and alternate rate matching scheme of the foregoing sequenceS when g=32 and performance obtained by using the sequential andalternate rate matching scheme when g=4. A horizontal coordinate is aquantity of information bits, and a vertical coordinate is asignal-to-noise ratio required when a block error rate is 0.001. A lowerrequired signal-to-noise ratio indicates better performance. It can belearned from FIG. 12 that when a quantity of to-be-punctured/shortenedbits is approximate to 1/4 code length, a puncturing/shortening patternthat is indicated by the foregoing symmetrical sequence and that is usedwhen g=32 is obviously better than the pattern used when g=4.

FIG. 13 is a schematic structural diagram of a rate matching apparatus1300 according to this application. The rate matching apparatus 1300includes:

-   -   an obtaining unit 1301, configured to obtain a coded bit        sequence, where the coded bit sequence includes g equal-length        groups, a quantity of coded bits in each group is N/g, N is a        mother code length of a polar code, N is an integral power of 2,        g is an integer greater than or equal to 4 and less than N, and        g is an integral power of 2;    -   a first determining unit 1302, configured to determine, based on        the groups, a bit position of a bit that needs to be        punctured/shortened in the coded bit sequence; and    -   a rate matching unit 1303, configured to obtain a coded bit in        the coded bit sequence except the bit that needs to be        punctured/shortened, to obtain a coded bit sequence obtained        after rate matching.

Optionally, the coding apparatus further includes:

-   -   a second determining unit 1304, configured to: if an actual code        rate is greater than a preset threshold, determine to use the        shortening rate matching method; or if an actual code rate is        less than or equal to a preset threshold, determine to use the        puncturing rate matching method, where the actual code rate is        K/M, K is a quantity of information bits, and M is the target        code length.

Optionally, the coding apparatus further includes:

-   -   a encoding unit 1305, configured to: place a frozen bit on a        polarized channel corresponding to the bit position of the bit        that needs to be punctured/shortened; in remaining polarized        channels, select a polarized channel with high reliability,        place an information bit on the polarized channel with high        reliability, and place frozen bits on the other polarized        channels; and map a to-be-coded bit to the information bit for        channel coding, to obtain the coded bit sequence.

The obtaining unit 1301 may be configured to perform step 402 in FIG. 4and a specific method in which step 402 is related in this application.The first determining unit 1302 may be configured to perform step 403 inFIG. 4 and a specific method in which step 403 is related in thisapplication. The rate matching unit 1303 may be configured to performstep 404 in FIG. 4 and a specific method in which step 404 is related inthis application. The second determining unit 1304 may be configured toperform step 401 in FIG. 4 and a specific method in which step 401 isrelated in this application.

FIG. 14 is a schematic structural diagram of another rate matchingapparatus 1400 according to this application. The rate matchingapparatus 1400 includes:

-   -   a memory 1401, configured to store a program; and    -   a processor 1402, configured to execute the program stored in        the memory, where when the program is executed, the processor        1402 performs the rate matching method described in the        embodiments of this application.

The rate matching apparatus 1300 and the rate matching apparatus 1400may be configured to perform the rate matching method described in thisapplication. For content about a manner of determining a bit position ofa to-be-punctured/shortened bit, a puncturing/shortening pattern, anapplication method of the puncturing/shortening pattern, how todetermine a rate matching manner, and the like, refer to the embodimentsof the rate matching method described above. Details are not describedherein again.

A receive end performs a corresponding reverse operation in a ratede-matching process. An LLR corresponding to a punctured/shortened bitposition is restored, and is respectively set to 0 or infinitely large,to implement rate de-matching. As shown in FIG. 15 , this applicationprovides a rate de-matching method, including the following steps:

1501. Obtain a log-likelihood ratio LLR of a to-be-decoded bit sequence,to obtain an LLR sequence.

1502. Determine a bit position of a punctured/shortened bit based ongroups.

1503. Restore an LIR value of a bit at the punctured/shortened bitposition, to obtain a log-likelihood ratio (LLR) sequence obtained afterrate de-matching, where the LLR sequence obtained after rate de-matchingincludes g equal-length groups, a quantity of LLRs in each group is N/g,N is a mother code length of a polar code, N is an integral power of 2,g is an integer greater than or equal to 4 and less than N, and g is anintegral power of 2.

Rate de-matching is a reverse process of rate matching. In the ratede-matching process, the bit position of the punctured/shortened bit isdetermined in manner the same as or corresponding to a rate matchingmanner performed by a transmit end. For example, a samepuncturing/shortening pattern (for example, a same sequence S) is used,and a quantity of groups is also the same as a rule of the transmit end.In the rate de-matching process, it is determined that apuncturing/shortening rate matching manner is also the same as apuncturing/shortening rate matching manner of the transmit end. Acorresponding rate matching manner may be determined based on an actualcode rate, and a rate de-matching manner corresponding to the ratematching manner is used to determine the bit position of thepunctured/shortened bit and correspondingly restore the LLR. A processof de-interleaving the restored LLR is a reverse process at the transmitend. For such specific content, refer to the description of the ratematching method embodiments.

FIG. 16 shows a rate de-matching apparatus 1600 according to thisapplication, including:

-   -   an obtaining unit 1601, configured to obtain a log-likelihood        ratio LLR of a to-be-decoded bit sequence, to obtain an LLR        sequence;    -   a determining unit 1602, configured to determine a        punctured/shortened bit position based on groups; and    -   a rate de-matching unit 1603, configured to restore an LLR value        of a bit at the punctured/shortened bit position, to obtain an        LLR sequence obtained after rate de-matching, where the LLR        sequence obtained after rate de-matching includes g equal-length        groups, a quantity of LLRs in each group is N/g, N is a mother        code length of a polar code, N is an integral power of 2, g is        an integer greater than or equal to 4 and less than N, and g is        an integral power of 2.

FIG. 17 shows another rate de-matching apparatus 1700 according to thisapplication, including:

-   -   a memory 1701, configured to store a program;    -   a processor 1702, configured to execute the program stored in        the memory, where when the program is executed, the processor is        configured to perform the rate de-matching method provided in        the embodiments of this application.

The rate de-matching apparatus 1600 and the rate de-matching apparatus1700 may be configured to perform the rate de-matching method describedin this application. For content about a manner of determining a bitposition of a punctured/shortened bit, a puncturing/shortening pattern,an application method of the puncturing/shortening pattern, how todetermine a rate matching manner, and the like, refer to the embodimentsof the rate matching method and the embodiments of the rate de-matchingmethod described above. Details are not described herein again.

FIG. 18 is a schematic structural diagram of a communications apparatus1800 according to an embodiment of this application (for example, acommunications apparatus such as an access point, a base station, astation, or a terminal). As shown in FIG. 18 , the communicationsapparatus 1800 may be implemented by using a bus 1801 as a general busarchitecture. The bus 1801 may include any quantity of interconnectedbuses and bridges based on specific application and an overall designconstraint condition of the communications apparatus 1800. The bus 1801connects various circuits together. These circuits include a processor1802, a storage medium 1803, and a bus interface 1804. The storagemedium is configured to store an operating system, to-be-sent data, andreceived data. Optionally, in the communications apparatus 1800, anetwork adapter 1805 and the like are connected by using the bus 1801and the bus interface 1804. The network adapter 1805 may be configuredto implement a signal processing function of a physical layer in awireless communications network, and send and receive a radio frequencysignal by using an antenna 1807. A user interface 1806 may be connectedto various user input devices such as a keyboard, a display, a mouse, ora joystick. The bus 1801 may further connect various other circuits suchas a timing source, a peripheral device, a voltage regulator, or a powermanagement circuit. These circuits are well-known in the art, and arenot described in detail herein.

The processor 1802 is responsible for managing the bus and generalprocessing (including executing software stored in a storage medium1803). The processor 1802 may be implemented by using one or moregeneral-purpose processors and/or dedicated processors. Examples of theprocessor include a microprocessor, a microcontroller, a DSMP processor,and other circuits that can execute software. The software should bebroadly construed as representation of instructions, data, or anycombination thereof regardless of whether the software is referred to assoftware, firmware, middleware, microcode, a hardware descriptionlanguage, or others.

As shown in FIG. 18 , the storage medium 1803 is separated from theprocessor 1802. However, persons skilled in the art easily understandthat the storage medium 1803 or any part of the storage medium 1803 maybe located outside the communications apparatus 1800. For example, thestorage medium 1803 may include a transmission line, a carrier waveformmodulated by using data, and/or a computer product separated from awireless node. These media may be accessed by the processor 1802 byusing the bus interface 1804. Alternatively, the storage medium 1803 orany part thereof may be integrated into the processor 1802, for example,may be a cache and/or a general-purpose register.

The processor 1802 may be configured to perform the rate matching methodor the rate de-matching method described in the embodiments of thisapplication. An execution process of the processor 1802 is not describedherein again.

In actual use, the rate matching apparatus and the rate de-matchingapparatus described in the embodiments of this application may beseparately independent devices, or may be an integrated device. Thedevice may be used as a transmit end to perform the rate matchingmethod, and may be used as a receive end to perform the rate de-matchingmethod.

In the examples described in the embodiments of this application, unitsand method processes can be implemented by electronic hardware or acombination of computer software and electronic hardware. Whether thefunctions are performed by hardware or software depends on particularapplications and design constraint conditions of the technicalsolutions. Persons skilled in the art may use a different method foreach specific application to implement the described functions.

In the several embodiments provided in this application, it should beunderstood that the disclosed apparatus and method may be implemented inother manners. The described apparatus embodiments are merely anexample. For example, the unit division is merely logical functiondivision and may be other division in actual implementation. Forexample, a plurality of units or components may be combined or may beintegrated into another system. Some steps in the method may be ignoredor not performed. In addition, coupling, direct coupling, or acommunication connection between the units may be implemented by usingsome interfaces, and these interfaces may be in an electronic form, amechanical form, or another form.

The units described as separate parts may or may not be physicallyseparate, and may be located in one place or may be distributed on aplurality of network units. In addition, functional units in theembodiments of this application may be integrated into one processingunit, or each of the units may exist alone physically, or two or moreunits are integrated into one unit.

All or some of the foregoing embodiments may be implemented by usingsoftware, hardware, firmware, or any combination thereof. When theembodiments are implemented by using software, the embodiments may beimplemented completely or partially in a form of a computer programproduct. The computer program product includes one or more computerinstructions. When the computer program instructions are loaded andexecuted on the computer, the procedure or functions according to theembodiments of the present invention are all or partially generated. Thecomputer may be a general-purpose computer, a dedicated computer, acomputer network, or another programmable apparatus. The computerinstruction may be stored in a computer readable storage medium, or maybe transmitted by using the computer readable storage medium. Thecomputer instructions may be transmitted from a website, a computer, aserver or a data center in a wired manner (for example, a coaxial cable,an optical fiber, or digital subscriber line (DSL)) or a wireless (forexample, infrared, wireless, or microwave) manner to another website,computer, server, or data center. The computer-readable storage mediummay be any usable medium accessible by a computer, or a data storagedevice such as a server or a data center into which one or more usablemedia are integrated. The usable medium may be a magnetic medium (forexample, a floppy disk, a hard disk, a magnetic tape, a USB flash drive,a ROM, or a RAM), an optical medium (for example, a CD or a DVD), asemiconductor medium (for example, a solid state disk (SSD)), or thelike.

The foregoing embodiments are merely intended for describing thetechnical solutions of the present invention, but not for limiting thepresent invention. Although the present invention is described in detailwith reference to the foregoing embodiments, persons of ordinary skillin the art should understand that they may still make modifications tothe technical solutions described in the foregoing embodiments or makeequivalent replacements to some technical features thereof, withoutdeparting from the scope of the technical solutions of the embodimentsof the present invention.

What is claimed is:
 1. A rate matching method, comprising: obtaining aPolar encoded bit sequence, wherein the Polar encoded bit sequence has acode length of N, and N is an integer power of 2, and N is greater thanor equal to 32; dividing the Polar encoded bit sequence into g groups, alength of each group is N/g, wherein g is 32; block interleaving the ggroups to obtain an interleaved bit sequence, wherein the interleavedbit sequence comprises g groups of bits, the g groups are orderedaccording to a sequence S after the block interleaving, each element inthe sequence S indicates a group number after the block interleaving;rate matching the interleaved bit sequence to obtain a rate matched bitsequence; and transmitting the rate matched bit sequence; wherein when atransmission code rate R is greater than a code rate threshold R0, therate matching the interleaved bit sequence to obtain the rate matchedbit sequence comprises: shortening (N-M) bits from end of theinterleaved bit sequence to obtain the rate matched bit sequence;wherein when a transmission code rate R is less than or equal to a coderate threshold R0, the rate matching the interleaved bit sequence toobtain the rate matched bit sequence comprises: puncturing (N-M) bitsfrom beginning of the interleaved bit sequence obtain the rate matchedbit sequence; wherein R=K/M and M is a positive integer smaller than N,K is positive integer, and wherein a value of the R0 is a less than 1/2and not less than 2/5.
 2. The rate matching method according to claim 1,wherein bit positions of first g/2 groups elements in the sequence S aresymmetrical to bit positions of last g/2 groups elements in the sequenceS.
 3. The rate matching method according to claim 1, wherein elements inthe sequence S are ordered in a priority order of puncturing orshortening the g groups.
 4. The rate matching method according to claim1, further comprising: generating a binary row vector u₁ ^(N) wherein u₁^(N)=(u₁, u₂, . . . , u_(N)), and K bit-positions of the binary rowvector u₁ ^(N) are occupied by K information bits; and encoding thebinary row vector u₁ ^(N) according an encoding formula, to obtain theencoded bit sequence; wherein the encoding formula is:x ₁ ^(N) =u ₁ ^(N) G _(N), wherein x₁ ^(N)=(x₁, x₂, . . . , x_(N)) isthe encoded bit sequence, and G_(N) is a polar code generating matrix ofN row and N columns.
 5. A device in a wireless communication network,comprising: a transmitter; a non-transitory memory storage comprisinginstructions; and one or more hardware processors in communication withthe non-transitory memory storage, wherein the one or more hardwareprocessors execute the instructions to: obtain a Polar encoded bitsequence, wherein the Polar encoded bit sequence has a code length of N,and N is an integer power of 2, and N is greater than or equal to 32;divide the Polar encoded bit sequence into g groups, a length of eachgroup is N/g, wherein g is 32; block interleave the g groups to obtainan interleaved bit sequence, wherein the interleaved bit sequencecomprises g groups of bits, the g groups are ordered according to asequence S after the block interleaving, each element in the sequence Sindicates a group number after the block interleaving; shorten (N-M)bits from end of the interleaved bit sequence to obtain a rate matchedbit sequence when a transmission code rate R is greater than a code ratethreshold R0; or puncturing (N-M) bits from beginning of the interleavedbit sequence to obtain the rate matched bit sequence when a transmissioncode rate R is less than or equal to the code rate threshold R0; whereinR=K/M and M is a positive integer smaller than N, K is positive integer,and wherein a value of the R0 is a greater than 1/2 and not greater than2/5; transmit, by using the transmitter and over a wireless network, asignal that comprises the rate matched bit sequence.
 6. The deviceaccording to claim 5, wherein bit positions of first g/2 groups elementsin the sequence S are symmetrical to bit positions of last g/2 groupselements in the sequence S.
 7. The device according to claim 5, whereinelements in the sequence S are ordered in a priority order of puncturingor shortening the g groups.
 8. The device according to claim 5, furthercomprising: generate a binary row vector u₁ ^(N), wherein u₁ ^(N)=(u₁,u₂, . . . , u_(N)), and K bit-positions of the binary row vector areoccupied by K information bits; and encoding the binary row vector u₁^(N) according an encoding formula, to obtain the encoded bit sequence;wherein the encoding formula is:x ₁ ^(N) =u ₁ ^(N) G _(N), wherein x₁ ^(N)=(x₁, x₂, . . . , x_(N)) isthe encoded bit sequence, and G_(N) is a polar code generating matrix ofN row and N columns.
 9. The device according to claim 5, wherein thedevice is a base station or a user terminal.
 10. A device in a wirelesscommunication network, comprising: a processor and a memory storingprogram instructions for execution; wherein, the processor is configuredto execute the program instructions to perform operations comprising:obtaining a Polar encoded bit sequence, wherein the Polar encoded bitsequence has a code length of N, and N is an integer power of 2, and Nis greater than or equal to 32; dividing the Polar encoded bit sequenceinto g groups, a length of each group is N/g, wherein g is 32; blockinterleaving the g groups to obtain an interleaved bit sequence, whereinthe interleaved bit sequence comprises g groups of bits, the g groupsare ordered according to a sequence S after the block interleaving, eachelement in the sequence S indicates a group number after the blockinterleaving; rate matching the interleaved bit sequence to obtain arate matched bit sequence; and transmitting the rate matched bitsequence; wherein when a transmission code rate R is greater than a coderate threshold R0, the rate matching the interleaved bit sequence toobtain the rate matched bit sequence comprises: shortening (N-M) bitsfrom end of the interleaved bit sequence to obtain the rate matched bitsequence; wherein when a transmission code rate R is less than or equalto a code rate threshold R0, the rate matching the interleaved bitsequence to obtain the rate matched bit sequence comprises: puncturing(N-M) bits from beginning of the interleaved bit sequence obtain therate matched bit sequence; wherein R=K/M and M is a positive integersmaller than N, K is positive integer, and wherein a value of the R0 isa less than 1/2 and not less than 2/5.
 11. The device according to claim10, wherein the device is a base station or a user terminal.
 12. Anon-transitory computer readable medium storing program codes thereonfor execution by one or more processors in a communication device,wherein the program codes, when executed by the one or more processors,cause the communication device to perform operations comprisingobtaining a Polar encoded bit sequence, wherein the Polar encoded bitsequence has a code length of N, and N is an integer power of 2, and Nis greater than or equal to 32; dividing the Polar encoded bit sequenceinto g groups, a length of each group is N/g, wherein g is 32; blockinterleaving the g groups to obtain an interleaved bit sequence, whereinthe interleaved bit sequence comprises g groups of bits, the g groupsare ordered according to a sequence S after the block interleaving, eachelement in the sequence S indicates a group number after the blockinterleaving; rate matching the interleaved bit sequence to obtain arate matched bit sequence; and transmitting the rate matched bitsequence; wherein when a transmission code rate R is greater than a coderate threshold R0, the rate matching the interleaved bit sequence toobtain the rate matched bit sequence comprises: shortening (N-M) bitsfrom end of the interleaved bit sequence to obtain the rate matched bitsequence; wherein when a transmission code rate R is less than or equalto a code rate threshold R0, the rate matching the interleaved bitsequence to obtain the rate matched bit sequence comprises: puncturing(N-M) bits from beginning of the interleaved bit sequence obtain therate matched bit sequence; wherein R=K/M and M is a positive integersmaller than N, K is positive integer, and wherein a value of the R0 isa less than 1/2 and not less than 2/5.